diff --git a/core/modules/rest/tests/src/Functional/ResourceTestBase.php b/core/modules/rest/tests/src/Functional/ResourceTestBase.php
index 49ef8e5..7fe1c91 100644
--- a/core/modules/rest/tests/src/Functional/ResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/ResourceTestBase.php
@@ -340,7 +340,7 @@ protected function assertResourceResponse($expected_status_code, $expected_body,
    *   The error response to assert.
    */
   protected function assertResourceErrorResponse($expected_status_code, $expected_message, ResponseInterface $response) {
-    $expected_body = $this->serializer->encode(['message' => $expected_message], static::$format);
+    $expected_body = ($expected_message !== FALSE) ? $this->serializer->encode(['message' => $expected_message], static::$format) : FALSE;
     $this->assertResourceResponse($expected_status_code, $expected_body, $response);
   }